Signors to telefonaktobolaget l



March 8, 1932.

Filed Sept. 24, 1929 In venwrs ififlsberky Patented Mar. 8, 1932 UNITEDSTATES MAURITZ VOS AND HAKAN AUGUST STER KY, OF STOCKHOLM, SWEDEN, AB-

PATENT OFFICE SIGNORS TO TELEFONAKTIEEBOLAGET L. M. EBICSSON, OFSTOCKEOLI, SWEDEN,

A. REGISTERED COMPANY OF SWEDEN MULTIPLE omrmwron.

' Application filed september 24, 1929, Serial No; 894,879, and inSweden October 8, 1928.

The present invention relates to a fI'B', quency converting electronvalve relay for the generation of oscillations of desired frequencywithout disturbances by additional undesired oscillations.

It has previously been proposed to use electron Valves in push-pullconnectionas frequency converters, the anodes of said valves being-thenconnected in [parallel in the common anode circuits, while thefundamental frequenciesto be converted are sup lations representing aconsiderable loss. of

energy and causing disturbing efl ects are produced in the anode circuitin addition to the desired oscillations. Another. considerabledisadvantage .of the known arrangement is that the lowest frequency isgenerated with the highest power, while the energy of the otheroscillations is less, the higher the frequency ofsaid oscillations.Further a the total output decreases very rapidly if it is attempted toincrease the load of the relay.

' The present invention has for its object to eliminate the saiddisadvantages. According to the invention the tuned oscillatory circuitsor impedances included in the anode circuit are connected with the gridcircuit by means of a feed back connection so devised as to retransfer,independently of the frequency, a constant fraction of the anodepotential, substantially eliminating the reaction of the anode voltageupon the control voltages of the relay, with equal phase to w the twogrids. Through the said compensation of the reaction of the anodevoltage on the control voltages the characteristic of the two-valverelay retains its symmetrical parabolic form also in the dynamic state,i. e. when the relay is loaded. It is hereby rendered possible to takeout the oscillations of different frequency generated in the anodecircuit with outputs of the same order of magnitude. If, by way ofexample, the two fundamental frequencies (a (0 are supplied to the twogrids, it is possible to take out from the anode circuit the fourtransformed frequencies 2e0 2G2, on (0 and m l'w with each "about onequarter of the total power. It is further,

throughthe constancy of the characteristic embodiment of the invention.Figure 2 is a circuit diagram of a modified embodiment. Figure 3 is acharacteristic diagram.

In the two embodiments shown the relay is composed of twothree-electrode tubes 1, 1' the anodes2,'2' of which are connected inparallel in relation to each other and connected to a common anodecircuit composed of a number of oscillatory circuits.- In the,embodiment according to Figure 1 the grids 3, 3 of the two tubesare'each connected to one terminal of the secondary coil 4 of atransformer, the primary winding 5 of which is supplied with thefundamental oscillation or oscillations to be converted. The middlepoint of the secondary winding is connected to the filament circuit overa grid biasing battery 6.

As the alternating potentials of the grids 3, 3' have mutually the sameamplitude but directly opposite phases the characteristics ofthe twotubes may in Figure 3 be represented by two curves 2', and i, runningsymmetrically in relation to the axis of ordinates. In the diagram Vrand V, represent the mutually equal and directly opposite controlvoltages of the tubes 1, 1. The relation between the anode currents a},i, of the two tubes and the supplied control voltages may beanalytically expressed through the formulas As regards the controlvoltages V and V the following relations exist:

in which V designates the anode alternating potential, V the controlalternating voltage, and a the amplification ratio of the tubes.

If it is assumed that two different fundamental frequencies in, (D aresupplied to the primary winding 5, which by way of example may be seriesconnected with two generators of said number of frequencies, one hasevidently V A1 Sin w t+ A2 Sin 032i According to Equations The resultingcontrol voltages are then V, =A sin co t A Sin 1 and V,= A sin w t-A sinwgt V,

The resulting anode current I, isobtained by insertion into theEquations (1) thus:

This resulting anode current is represented in the diagram, Figure 4, bythe parabolic curve drawn in full lines. In most cases one may in thelast equation neglect terms of higher order than the second for whichreason the curve I may be practically considered asau exact parabola.One may now in the Formula (1) immediately neglect terms of the fourthdegree and of higher orders and obtains thus for the resulting anodecurrent I 20 i 202 (A1 Sin (E li lAg Sin (.020 20 U A (1 cos 2w t)-| U A(1 cos 20: 1,) 2021 11142 [OOS(w w )t CO5 ((01 Cdg fl The anode currentcontains thus the fre- (lHGIlClQS 210 20);, (01 m {111(1 (0 m Theanode-circuit includes a number of oscillatory circuits which are tunedeach to one of said frequencies. Said 0s *illatory circuits are in theshown embodiment mutually series connected and consist each of aninductance 7 and a capacity 8 connected in parallel. The inductance 7are inductively connected each to one compensating coil 9, whichcompensating coils are series connected in relation to each other and tothe grid biasing battery 6. By the retransfer by means of the coils 9the two grids 3, 3 are supplied with mutually equal compensatingpotentials of the same phase sequence. Said compensating potential isinthe Formulas (3) and (4) represented by the term 8V The factor 8 inthis term is so adjusted by a suitable selection of the degree ofcoupling between the coils 7 and 9 ti at the reaction of the anodepotential upon the control voltage is exactly compensated as abovedescribed. The different anode circuit frequencies are tapped off fromthe appertaining tuned oscillatory circuits over the terminals 10.

If the two fundamental frequencies m m: are obtained from mutuallyindependent generators it may occur that a higher harmonic of the onefundamental oscillation in the grid circuit so interferes with the otherfundamental oscillation that an interfering tone of low frequency isproduced in the anode circuit. If, by way of example, the onefundamental frequency m is intended to have twice the value of the otherone, the first of the higher harmonics of the latter fundamentalfrequency may on account of involuntary variations in the relationbetween the fundamental frequencies interfere with w; and thus cause adisturbing tone. The two frequencies w +co and i m occurring in theanode circuit are also dependent on the variations in the frequencies oiand 0 supplied to the grids.

This inconvenience will be entirely eliminated by the embodiment shownin Figure 2. This embodiment differs from the above described onlytherein that the secondary wind ing of the input transformer is dividedinto two halves 11, 11 and that a back coupling coil 12 and12respeetively is included in series with each half. Said two backcoupling coils are inductively coupled to one of the oscillatorycircuits included in the anode cir cuit. The back coupling coils 12, 12are over the grid biasing battery 6 both connected to the filamentcircuit.

In this embodiment only a single fundamental oscillation with thefrequency w is supplied from the outside which frequency is thussupplied to the primary terminals of the input transformer. The otherfundamental frequency is, on the other hand, obtained by means of theback coupling of one of the multiple frequencies cccuring in the anodecircuit through the intermedium of the coils 12, 12'. In the circuitarrangement shown in Figure 2 the second harmonic 2w generated in theanode circuit is in this way transferred back to the V actly the samemutual proportion.

grid circuit and is there superimposed upon the fundamental oscillationsupplied from the outside. The oscillatory circuit for 2c) is thus inthis case connected to the grid circuit through a double back coupling,i. e. by means of a compensating coil 9 through which the two grids 3, 3obtain compensating potentials of mutually equal phase sequence and ofthe frequency 2m and also by means of the two back coupling coils 12, 12which transfer the frequency 20: to the two grids with mutually equalamplitudes but with opposite phases.

In the example shown in Figure 2, thus:

' In the anode circuit the frequencies 2m =4a), 2:0 w +w =3m and (o w =ware then obtained.

If desired, one may of course retransfer more than one of thecombination tones occuring in the anode circuit. If, by way of example,the grid circuit is supplied with the two oscillations w and 4a)generated in a separate generator and the two oscillations 3m and 5a)are retransferred from the anode circuit, oscillations of thefrequencies 3 510, 7 w and 100) may be obtained in the anode circuit.For this purpose the retransfer coils 12, 12 are connected to the twooscillatory circuits which are tuned to the frequencies and The circuitarrangement according to Figure 2 offers the advantage in comparisonwith the first described arrangement that in case of fluctuations in thefundamental frequency supplied from the outside all frequenciesgenerated in the anode circuit will vary in exigher harmonics of thefundamental frequency, which may occur, will thus under all conditionseither completely coincide with or considerably differ from thefrequencies retransferred from the anode circuit to the grid circuit andwill thus not cause disturbing tones. 1

If it is desired to obtain oscillationsof a still higher frequency oneof the frequencies generated in the anode circuit may be tapped ofl:'therefrom and used as fundamental frequency in another static converteraccording to Figure 2 etc. Two of the frequencies in the anode circuitmay also be tapped off and together supplied to a converter according toFigure 1. In this manner a plurality of converters may be connected incascade, arbitrary multiples of a given fundamental frequency being thenobtainable. If the frequencies 30) and 4w, by way of example, are tappedoff from the anode circuit in Figure 2 and supplied to the input side ofa succeeding converter according to Figure 1 the frequencies 6m, 8m, 7mand w are obtained in the anode circuit of the latter. If again only thefrequency 4w is tapped off and introduced on the 2. Any desiredfrequency'may be obtained in the anode circuit by a suitable selectionof said fundamental frequencies.

3. Just the desired frequency maybe tapped off from the anode circuitindependently of other frequencies. 11

4. Any desired frequency may be gener-. ated by the connection ofseveralconverters in cascade. o a

.5. The generated frequencies may be obtained practically free fromhigherhar monics.

6. The obtainable power output is nearly the same in the differentoscillatory circuits included in the anode circuit in contradistinctionto hitherto known valve generators in which the power output veryrapidly decreases with a rising frequency of the higher harmonics.

. 7. 'A multiple generator according to the invention may be exactlydimensioned on the basis of an exact theoretical precalculation.

The features according to 3 and 6 are essentially due to the fact thatthe multiple generator accordingto the invention doesnot operate asan-oscillator in the ordinary mean.-

ing of the word, i. e. it does not operate with back-coupling of thekind usually applied in an ordinary valve generator. Incontradistinction thereto also-the inner back coupling in the valves inthe present arrangement is compensated bymeans of the compensating coils10. i

. On account of said characteristic features thecircuit arrangementaccordin to the invention is especially suitable-to e applied, by way ofexample, in telephone systems in which high frequency oscillations areused as carrierwaves to transmit speech waves along telephone lines. Anentire line s sterm may then be fed with oscillations which are obtainedfrom a single common fundamental frequency by means of staticconversion. Said fundamental frequency may be of a comparatively lowfrequency,ly1ng, by way of example, within the range of voice fre--quencies and may then be converted to higher frequencies byconnectingtwo or several frequency converting multiple generators incascade according to the invention. A fundamental oscillation with acompletely constant frequency may, by way of example, be obtained bymeans of a=generatorof the tuned fork type. The different high frequentoscillationson the lines are-thereby also obtained with'a completelyconstant frequency.

The compensation of the reaction of the anode -load upon the controlvoltages of the valve may also take place in other manner than by'theconnection of the anode circuit to the grid circuit as above described.By way of example, said compensation may be brought about by the use ofspecial electron valves, suchas shielded grid valves or pentode valvesor the like, in which a shielding grid is disposed between the controlgrids and theanodes and said shielding grid is maintained at a constantpotential.

WVeclaim 1. A frequency converting electron valve relay comprising twogrids, means for supplying fundamental oscillations with oppositephaseto said grids,two anodes connected in parallel in a common anodecircuit, a number-of impedances tuned to different frequencies andincluded in said anode circuit, and feed back connection adapted toretransfer, independently of the frequency, a constant fraction of theanode potential, substantially eliminatingthe reaction of the anodevoltage upon the control voltages, with equal phase tothe two grids.

.2. A frequency converting relay as claimed in claim 1, characterized bythat the grid biasing voltage is negative and substantially equal to thepart of the constant anode potential.

A frequency converting electron valve relay comprising two grlds, meansfor supplying fundamental oscillations with opposite phase to saidgrids, two anodes connected in parallel'in a common anode circuit, anumber of impedances tuned to different frequencies and included in saidanode circuit, and

a number of feed back coils each connecting one of said tuned impedancesinductively with the grid circuit so as to retransfer a potential of'thecorresponding frequency, substantially eliminating the reaction of theanode voltage uponthe control voltages, with equal phase to the twogrids.

4. A frequency converting relay as claimed in claim 3, characterized inthat the compensating'coils are connected into circuit between thefilament circuit and the middle point of an impedance which is connectedup between the two grids and upon which the fundamental frequencies areimpressed.

In testimony whereof weaflix our signatures.

MAURITZ VOS.

HZKAN KARL AUGUST STERKY.

